Note:

Pre-market and after-hours trading on the same trading day will be taken into account when calculating how many day trades are left.
Selling shares owned from a previous day doesn’t count as a day trade.

1, At the start of Monday, you own 0 shares of ABC stock and have 0 day trades.

Buy 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Sell 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Number of Day Trades : 1

2, At the start of Monday, you own 0 shares of ABC stock and have 0 day trades.

Buy 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Buy 50 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Sell 150 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Number of Day Trades: 1

3, At the start of Monday, you own 0 shares of ABC stock and have 0 day trades.

Buy 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Sell 50 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Sell 50 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Number of Day Trades : 1

4, At the start of Monday, you own 0 share of ABC stock and have 0 day trades.

Buy 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Buy 50 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Sell 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Sell 50 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Number of Day Trades: 1

5, At the start of Monday, you own 0 shares of ABC stock and have 0 day trades.

Buy 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Sell 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Buy 50 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Sell 50 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Number of Day Trades: 2

6, At the start of Monday, you own 100 shares of ABC stock and have 0 day trades.

Sell 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Buy 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Number of Day Trades: 0

7, At the start of Monday, you own 100 shares of ABC stock and have 0 day trades.

Sell 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Buy 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Sell 100 shares of ABC --- Monday (4:00 AM - 8:00 PM EST)

Number of Day Trades: 1